doraemon python module

Chapter VI module

6.1 module

• Built-in module, it has provided the function of internal python

import sys

• Third-party modules, download / install / use

# Pip.exe directory where it is added to the environment variable 
PIP install the module name of the installation of   # example: pip install xlrd

• Custom Module (write your own functions)

  • xxx.py

  def f1():
      print(123)
      
  def f2():
      print(125)

  • x1.py

  # Content-defined function called from inside the 
  Import xxx 
  xxx. F1 () 
  xxx. F2 ()

   

6.2 sys

python interpreter related data

• sys.getrefcount, obtaining a worthy application count

• sys.getrecursionlimit, python supported by default the number of recursive

• sys.stdout.write-->print

Print progress bar # 
Import Time 
for I in Range ( . 1, 101): MSG = "% S %%" % I Print ( MSG, End = "") . Time SLEEP ( 0.05)
    
    
    

• sys.argv

# Allow users to execute scripts passed to delete the file path, internally to help users delete the directory 
Import SYS 
C: \ Python36 \ python36. EXE D: / code / s21day14 / 7. . Module parameter passing Py D: / the Test 
SYS. = the argv [ D: / code / s21day14 / 7. The module transfer parameters. Py, D: / Test] 
path = SYS. the argv [ . 1] Impor the shutil the shutil. rmtree ( path)

• sys.path, default pythn to import the module, it will follow one by one sys.path looking for the Road King

Import SYS 
. SYS . path the append ( 'D: \\') 
Import XXX   # referenced modules other than the default path

• json

json is a special string [like a long list / dictionary / string / numeric / genuine]

Why do they do:

1. In addition to convenience python interpreter to run code written in python

2. Other code written facilitate interpreter, it is converted into something recognizable python

Import json 
# serialized, converted to the value of the python json format string 
V = [ . 11, 22 is, . 4, { "K1": "V2"}, True, "SAF"] 
V1 = json. dumps ( V) 
Print ( V1) # deserialize the json python string format is converted to data type V2 = '[' Alex ', 123]' Print ( type ( V2)) V3 = json. loads ( V2) Print ( v3, of the type ( v3))

 

6.3 the

• Size os.stat ( 'filename') .st_size read the file

import os 
file_size = os.stat('刘丹妮.mp4').st_size
​
read_size = 0
with open('刘丹妮.mp4',mode = 'rb') as f1,open('a.mp4',mode='wb') as f2:
    while read_size < file_size:
        chunk = f1.read(1024)#每次最多读取1024字节
        f2.write(chunk)
        read_size += len(chunk)
        val = int(read_size/file_size*100)
        print('%s%%/r' %val,end="")

• os.path.exists (path), if the path exists, returns True; if the path does not exist, returns False

• os.path.abspath (), get a file absolute path

path = '20190409_192149.mp4' 
import os
v1 = os.path.abspath(path)
print(v1)

 

• os.path.dirname, get the parent directory path

• import os
  v = r"D:\code\s21day14\20190409_192149.mp4"
  ​
  print(os.path.dirname(v))

• Stitching os.path.join, path

import os
path = "D:\code\s21day14" # user/index/inx/fasd/
v = 'n.txt'
​
result = os.path.join(path,v)
print(result)
result = os.path.join(path,'n1','n2','n3')
print(result)

• os.listdir, to view a directory of all the files [first floor]

• import os
  ​
  result = os.listdir(r'D:\code\s21day14')
  for path in result:
      print(path)

• os.walk, to view a directory of all the files [all levels]

Import os the Result = os. Walk ( r'D: \ code \ s21day14 ') for A, b, c in the Result: # A, are viewing the directory b, files in this directory folder c, files in this directory for Item in C: path = OS. path. the Join ( A, Item) Print ( path)



    
    
        
        

• os.makedirs, create directories and subdirectories

import os 
file_path = r'db/sf/sf/er/xxx.txt'
​
file_folder = os.patn.dirname(file_path)
if not os.path.exists(file_path)
 os.makedirs(file_folder)
    
with open(file_path,mode='w',encoding='utf-8') as f:
    f.write('asdf')

• os.rename, rename

import the 
them. rename ( 'sb', '250')

 

6.4 Special supplement

= v1 r "D: \ code \ s21day14 \ n1.mp4" ( recommended) 
Print ( v1) v2 = "D: \\ code \\ \\ n1.mp4 s21day14" Print ( v2) #python in execution process, the \ very sensitive, according to the case to write, it is easy on the error system, is about to make the role of r \ are considered merely \, to distinguish \ n this

• shutil

import statement the shutil 
the shutil. rmtree ( path)